1. Field of the Invention
The present disclosure relates to a keypad with a light guide pad, and more particularly to a keypad with a light guide pad connectively attached with a pattern sheet printed with a letter or a figure to an upper side of a light guide pad connectively attached with a light source for generating light and a sensor for measuring an quantity of light, to determine an operation signal by detecting a difference of quantity of light passing the light guide pad in response to operation of the pattern sheet.
2. Description of Related Art
A keypad is a switching device configured for a user of a mobile phone and/or terminal to generate a signal.
A typical keypad is illustrated in FIG. 1 The keypad includes a key top 180 printed or engraved with a recognition symbol including a number and/or a letter, and a base 120 positioned underneath a front housing 140 connected via a connector 130.
The keytop 180 and the base 120 are coupled to the front housing 140 forming an exterior look of a mobile phone to form a key button 100, and the keytop 180 protrudes to an external side of a hole formed at the front housing 140.
A printed circuit board (PCB. 160) attached with a dome switch 150 is coupled at a predetermined distance from the keytop 180 to a lower end of the keytop 180 and the base 120. The keytop 180 is formed thereunder with a protruder 110 for pressing the dome switch 150, and a light source 170 is formed at a rear surface of the keytop 180 to allow a user to recognize the letter or a figure printed at a periphery of the keytop 180 even at night.
The light source 170 primarily uses an LED, and the recent trend for the light source 170 is to use a thin film EL sheet that is slim, uniform in light and consumes less power.
However, the conventional keypad suffers from a disadvantage in that light generated from the light source 170 is irradiated to an entire area of the keypad to vanish into a space between the buttons 180 and to provide a difficulty in concentratively illuminating the button 180 alone.
There is another disadvantage in the conventional keypad in that the light sources 170 are respectively mounted at the PCB 160 between the buttons 180 of the keypad to inevitably illuminate the entire area of the keypad, thereby necessitating installation of 12 to 20 or more light sources 170, for example, whereby the manufacturing cost increases and the power for the mobile phone and the terminal is over-spent.
Still another disadvantage is that there occurs a light deviation where ambient of the light source 170 is bright while a distanced area from the light source 170 is dark.